Virus in my flower border
I suspect the problem is a disease rather than a virus and most likely a soil borne one. I would suggest you try Grow Boost from Harrod Horticultural. This contains a beneficial fungi called Trichoderma. This out competes and protects plants from soil borne diseases. It is supplied in a sachet and you water it in. It is not harmful to any insects, wildlife or plants. I would suggest you water some into the infected bed now and repeat next spring prior to planting. It is more of a preventative treatment than curative, so may stop all the infestation now but will help build up beneficial fungi in the soil to counter the problem in the future. I hope this helps.